1. Field of the Invention
This invention relates to an improved blowout preventer ram actuating and locking apparatus for a ram-type blowout preventer used in oil and gas drilling operations. Ram-type blowout preventers are part of a pressure control system used in oil and gas drilling operations to control unexpected well bore pressure spikes or "kicks" as they are commonly referred to in the industry.
The blowout preventer has a body with a vertical bore and a pair of laterally disposed opposing bonnet assemblies. Each bonnet assembly includes a piston that is laterally moveable within the bonnet assembly by pressurized hydraulic fluid. When these pistons are moved to a closed position, commonly referred to as "closing the blowout preventer" or "closing the rams", the vertical bore of the blowout preventer is sealed and the "kick" is contained. Replaceable sealing elements called "rams" are mounted on the ends of the pistons that extend into the blowout preventer bore. These "rams" are available in a variety of configurations designed to seal the blowout preventer bore when the opposing pistons are moved to their closed position. One type of ram has ends designed to seal around pipe of a specific size in the blowout preventer bore when the blowout preventer is "closed." Other rams are configured to shear any pipe in the blowout preventer bore during closing while still others are designed to seal around a range of pipe sizes.
It is imperative that the rams stay closed during a kick until the well bore pressure can be controlled. The well bore pressure can reach several thousand pounds per square inch during a "kick." In the event that hydraulic control pressure is lost or removed, the rams could be forced open by the well bore pressure and cause an uncontrolled pressure well bore release or "blowout." In order to ensure the rams remain closed and the well bore pressure contained during a hydraulic system failure, an automatic blowout preventer ram lock is required. It is such an automatic blowout preventer ram lock to which the present invention is directed. As noted above the blowout preventer rams are available in a variety of configurations. Additionally, the rams themselves experience a considerable amount of wear during their normal use. These factors require that an automatic blowout preventer ram lock be capable of locking the ram and its associated piston in a range of positions depending on the type of ram being used and the amount of wear on the ram.
Numerous locking devices for use with ram-type blowout preventers have been used since the early days of the industry. Problems associated with these prior blowout preventer ram locks include complexity of operation, expensive to manufacture and maintain and adding unnecessary width to the blowout preventer assembly. The automatic blowout preventer ram lock of the current invention offers a substantial improvement by offering a simple, easy to maintain ram lock that is considerably more compact than similar ram locks.
2. Description of Related Art
Various types of ram lock designs are well known to those of ordinary skill in the art. These designs all fail in one or more respects to address the problems described.
U.S. Pat. No. 3,242,826 to W. W. Smith shows an early version of a blowout preventer ram lock. This apparatus can only lock the ram in a single position.
A number of designs have used a ratcheting apparatus that cooperates with the mating teeth formed on the ram piston or an extension thereof. Notable among these are U.S. Pat. Nos. 3,941,141 (Robert); 4,076,208 (Olson); 4,290,577 (Olson); 4,293,115 (Parks, Jr. et al.) and 4,840,346 (Adnyana et al.)
Another group of designs has used a wedge shaped locking member that cooperates with a tapered end on the rear of the ram to lock the ram. These include U.S. Pat. Nos. 4,969,627 (Williams III); 4,523,639 (Howard, Jr.) and 4,601,232 (Troxell, Jr.).
A final group has relied on various wedge shaped members that are axially moveable to lock between a mating surface on the ram and the bonnet housing. These include U.S. Pat. Nos. 4,305,565 (Abbe); 4,519,571 (Jones et al.); 5,025,708 (Smith et al.) and 5,575,452 (Whitby et al.)